PID's with modbus communication

How the motor speed will control through PID's with modbus communication.

please tell me the procedure from basics. i didn't know about PID.

what are the parameters i should be use?

Hi

Please tell us what r you looking for .

Do you want to control VFD on PID ir the motor RPM with PID.

Please explain ur requirement little clear.

Hi,

See This example:

SINAMICS G: Speed control of a G120P using S7-300/400 (STEP 7 V5) with MODBUS RTU

About the control function itself. We should understand what you need but as a background info:

If you are thinking about implementing the PID in the PLC, I did not find any example, but see this manual that details  PID operation well:

PID Temperature Control.

Note: Basically the PID set up as usual, but if you use the drive speed as "Manipulating Variable" then the PID output should go to the Speed SP to the drive. 

If you are thinking about implementing PID in the Drive, see this link as info:

MICROMASTER 4 (MM4), SINAMICS G120 (CU2x0x): Configure the feedback signal when using PID control

please go a little more in detail.. What kind of Hardware are you using? in Step7 there is a PID-Function block which can be used. You have to give directly an input like temperature, motor speed, etc.. and get an output in WORD format for output on modbus.. For modbus I'm not the right contact person but the output of PID block can for sure be switched on modbus.

Attached a picture of example FB41!

please check out the help for FB41 to see the complete definition of I/O.

Give another post when you are not using Step7. (I think this question is anyway asked in the wrong thread)

Thanks for u r ,reply

                                    I need to control the speed of the motor from the PID and is it possible to  control the motor speed without feed back value?

In my example the SPEED is the PID SETPOINT  input and  the actual value is the FEED BACK value.

Here just i am taken some value in the FEED BACK value with out connecting the encoder.Is it possible to do for motor controlling?

Please suggest me how could i control the motor speed with out using the encoder.I am new with this PID

Thank u.

There must be a value for feedback input otherwise the PID-Regulator doesn't know on which value the output must be setted. 

For sure you can write in feedback a static value like "100". But then the output for motor speed is allways 100 and the regulator is completely unnecessary..

s23

Thanks for u r ,reply

                                    I need to control the speed of the motor from the PID and is it possible to  control the motor speed without feed back value?

In my example the SPEED is the PID SETPOINT  input and  the actual value is the FEED BACK value.

Here just i am taken some value in the FEED BACK value with out connecting the encoder.Is it possible to do for motor controlling?

Please suggest me how could i control the motor speed with out using the encoder.I am new with this PID

Thank u.

 Hi,

It is up to your application. I am not sure I understand what do you try to do! See the manual below about what data you usually send to drive and what data do you recieve. What drive do you use and what interface? What is the control function you need to implement?

 Anyways you should be able to read the actual motor Speed in the PLC via profibus/profinet/Modbus etc..See for example SINAMICS G120, CU240B/E-2 Control Units under chapter "2.5 Communication, fieldbus interface (USS, Modbus)" about how you can talk to the drive via Modbus(and what data you can set up as interface). Profidrive interface is far simpler than MODBUS, see this in the above manual chapter "2.6 PROFIdrive communication (PROFIBUS)".

About encoderless control see this old article :

SENSORLESS VECTOR CONTROL (SVC) Application Note